Depreciation factor equation to evaluate the economic losses from ground failure due to subsidence related to groundwater withdrawal

Subsidence due to groundwater withdrawal is a complex hydrogeological process affecting numerous cities settled on top of fluviolacustrine deposits. The discrete spatial variation in the thickness of these deposits, in combination with subsidence due to groundwater withdrawal, generates differential settlements and aseismic ground failure (AGF) characterized by a welldefined scarp. In cities, such AGF causes severe damages to urban infrastructure and considerable economic impact. With the goal of arriving to a general criterion for evaluating the economic losses derived from AGF, in the present work we propose the following equation: ELi = PVi*DFi. Where PVi is the value of a property “i”, and DFi is a depreciation factor caused by structural damages of a property “i” due to AGF. The DFi is calculated empirically through: . This last equation is based on the spatial relations of coexistence and proximity of property polygons and the AGF axis. The coexistence is valued as the quotient of the affectation area divided by the total area of the involved property;and the proximity to the AGF axis is expressed as the inverse of the perpendicular distance from the centroid of the property polygon to the AGF axis. The sum of these terms is divided by two to determine the percentage that affects the property value (PVi). These equations are relevant because it is the first indicator designed for the discrete assessment of the economic impacts due to AGF, and can be applied to real estate infrastructure from either urban or rural areas.

Numerical simulation of cyclic behavior of double sand lenses and corresponding liquefaction-induced soil settlement

A two-dimensional numerical model was used to explain the liquefaction mechanism of double sand lenses and the corresponding soil deformation due to the cyclic loading. Moreover, in order to investigate the influences of the soil characteristics and input loading data a parametric study was carried out on the essential parameters affecting the soil settlement, and so the variation of these parameters with the corresponding displacements was mainly examined. At last, the results obtained from the numerical analyses of double sand lenses and a continuous sand layer with similar characteristics were compared with those of an estimating method proposed by ISHIHARA and YOSHIMINE. The comparisons show that the settlements due to liquefaction of the continuous sand layer in both numerical and the estimating method are in a good agreement with and are obviously greater than those of double sand lenses.

Seismic intensity investigation of the 2001 M=6.0 Yajiang-Kangding earthquake and discussion on its background of seismogenic structures

An M=6.0 earthquake occurred on February 23, 2001 in the western Sichuan Province, China. The macro seismic epicenter situated in the high mountain-narrow valley region between Yajiang and Kangding counties. According to field investigation in the region, the intensity of epicentral area reached VIII and the areas with intensity VIII, VII and VI are 180 km2, 1 472 km2 and 3 998 km2, respectively. The isoseismals are generally in elliptic shape with major axis trending near N-S direction. The earthquake destroyed many buildings and produced some phenomena of ground failure and mountainous disasters in the area with intensity VIII. This event may be resulted from long-term activities of the Litang fault and Yunongxi fault, two main faults in the western Sichuan. The movements between the main faults made the crust stress adjusted and concentrated, and finally the earthquake on a secondary fault in the block released a quite large energy.